The present invention generally relates to heat recovery devices and, more particularly, to a control system for heat recovery coils.
Although electric power is utilized in diverse ways in the economy and demand remains high at all times, the demand for electric power nevertheless fluctuates markedly during the course of a day. Business demand is high throughout daylight hours in the operation of stores and offices, but diminishes significantly thereafter. Residential demand is highest in the evening hours. Industrial demand is relatively steady and high at all times. Other demands, such as for urban transportation, peak at differing times. Additionally, demand can vary greatly seasonally and with short-term changes in the weather. For example, electricity usage soars on abnormally hot days due to widespread use of air conditioning equipment.
In an optimized power utilization system, all such demands would be complementary and thus provide a substantially constant power requirement which could be served readily by the various sources of electric power in a readily predictable manner. In reality, however, electric power demand is nowhere near constant.
The uneven demand for electric power requires that power generation capacity be sufficiently great to accommodate the maximum instantaneous demand. This, in turn, leads to uneconomic operation of generally over-sized electric power generation facilities. One approach to this problem has been the encouragement of off-peak usage of electric power in an effort to restructure the demand pattern. Another approach has been the installation of additional generating facilities intended for use during the periods of peak power demand. For example, an electric utility may lease one or more gas turbine electric generators in order to bring on-line more power generation capacity during warmer months of the year.
One such prior art gas turbine electric generator is illustrated in FIG. 1 and indicated generally at 10. The turbine 10 is housed within a structure 12 having an air inlet 14 and an exhaust stack 16. The gases exiting the top of the exhaust stack 16 are extremely hot, typically in the neighborhood of 900xc2x0 F.
This exhausted heat is energy that is not being utilized by the system, thus drastically lowering the efficiency of the turbine 10. This heat represents energy that is consumed by the turbine 10 but not turned into useful generated electricity.
Obviously, it would be desirable to recover the energy being lost as heat from the turbine 10 (or any other system that produces wasted heat exhaust) and convert this heat to a useful form. The present invention is directed toward this goal.
The present invention relates to a method and apparatus for selectively introducing one or more sets of heat transfer coils into the path of heated gasses to facilitate reclamation of at least some of the heat for transduction into useful energy. One form of the present invention is a set of coils adapted to circulate a heat-conducting fluid under pressure. The coils are in fluidic communication with a fluid chilling assembly. The coils are further adapted to be partially or completely introduced into an environment containing hot gasses (a hot zone), wherein heat is transferred from the hot gasses to the fluid circulating in the coils. The heated fluid is circulated into the chillers, where the heat is removed and transduced into a conveniently useful form of energy, such as electricity. The coils may b e only partially introduced into the hot gasses so as to optimize t he heat transfer to the coils and to prevent overheating of the heat conducting fluid and damage to the coils. The extent to which the coils are introduced into the hot gasses is variable and is a function of the temperature of the gasses and the fluid in the coils. In t he event of a power or control failure, the coils may be provided with a failsafe configuration to automatically remove them from t he hot gas environment.
One object of the present invention is to provide an improved heat energy reclamation system with an automatic failsafe to guard against accidental overheating.
Related objects and advantages of the present invention will be apparent from the following description.